Rett syndrome (RTT), an X-linked neurodevelopmental disorder, is the leading cause of mental retardation and autistic features in females. RTT results from loss-of-function mutations in the gene encoding methyl-CpG-binding protein 2 (MeCP2), which binds to target DNA and recruits Sin3A and histone deacetylases to silence transcription. Although MeCP2 is ubiquitously expressed, the Rett phenotype is predominantly neurological; I hypothesize that loss of MeCP2 function leads to altered expression of neuronal genes, and that the neural specificity of the phenotype is mediated by interactions of MeCP2 with neuronal-specific factors. The overarching goal of this proposal is to test these hypotheses by evaluating the effects of MeCP2 on neuronal gene expression and to probe for interactions with neuronal genes to uncover potential novel functions. Analysis of a mouse bearing a transgene for human MeCP2 under the endogenous promoter will complement ongoing analysis of a mouse line bearing a loss-of-function mutation. Microarray analysis will help identify downstream targets of MeCP2. Finally, insight into MeCP2 function should be gained by identifying proteins that interact with the C-terminal end of MeCP2, which has recently been shown to contain homology to neural-specific transcription factors.